AS4C64M8D2
ODT (On Die Termination)
On Die Termination (ODT) is a feature that allows a DRAM to turn on/off termination resistance for each DQ,
DQS/DQS#, DM signal via the ODT control pin. The ODT feature is designed to improve signal integrity of the
memory channel by allowing the DRAM controller to independently turn on/off termination resistance for any or all
DRAM devices.
The ODT function is supported for ACTIVE and STANDBY modes. It is turned off and not supported in SELF
REFRESH mode.
Figure 4. Functional representation of ODT
VDDQ
VDDQ
VDDQ
SW1
SW2
SW3
Rval1
Rval2
Rval3
DRAM
Input
Buffer
Input
pin
Rval1
SW1
Rval2
SW2
Rval3
SW3
VSSQ
VSSQ
VSSQ
Switch (sw1, sw2, sw3) is enabled by ODT pin.
Selection among sw1, sw2, and sw3 is determined by “Rtt (nominal)” in EMR.
Termination included on all DQs, DM, DQS, DQS# pins
Table 9. ODT DC Electrical Characteristics
Parameter/Condition
Symbol
Min.
Nom.
Max.
Unit Note
Rtt effective impedance value for EMRS(A6,A2)=0,1;75Ω
Rtt effective impedance value for EMRS(A6,A2)=1,0;150Ω
Rtt effective impedance value for EMRS(A6,A2)=1,1;50Ω
Ω
Ω
Ω
%
Rtt1(eff)
Rtt2(eff)
Rtt3(eff)
60
120
40
75
150
50
-
90
180
60
6
1
1
1
2
Rtt mismatch tolerance between any pull-up/pull-down pair Rtt(mis)
-6
NOTE 1: Measurement Definition for Rtt(eff):
Apply VIH (ac) and VIL (ac) to test pin separately, then measure current I(VIH(ac)) and I(VIL(ac)) respectively.
V (ac) V (ac)
IH
IL
Rtt(eff)=
I(V (ac))-I(V (ac))
IH
IL
NOTE 2: Measurement Definition for Rtt (mis): Measure voltage (VM) at test pin (midpoint) with no load.
2xVM
VDDQ
Rtt(mis)=
1 100%
Confidential
13
Rev. 1.0
Feb. /2014
ALSC [ ALLIANCE SEMICONDUCTOR CORPORATION ]
